On a pterosaur jaw from the Upper Jurassic of Tendaguru (Tanzania)

A short section of a mandibular symphysis is the first cranial fossil of a pterosaur to be reported from the Upper Jurassic of Tendaguru, Tanzania. It is made the holotype of a new dsungaripteroid pterosaur, Tendaguripterus recki n. gen. n. sp. All previously named pterosaur taxa from Tendaguru are shown to be nomina dubia. The pterosaur assemblage from Tendaguru contains a "rhamphorhynchoid", as well as the dsungaripteroid, and is similar in its systematic composition to other Late Jurassic pterosaur assemblages from Laurasia. The diversity and broad distribution of dsungaripteroids in the Late Jurassic suggests that the group was already well established by this time. Der erste Schädelrest eines Flugsauriers aus dem Oberjura von Tendaguru in Tansania wird beschrieben. Bei dem Fundstück handelt es sich um ein bezahntes Unterkieferbruchstück aus der Symphysenregion. Der Fund gehört zu einem neuen Taxon, das als Tendaguripterus recki n. gen. n. sp. bezeichnet und zur Überfamilie Dsungaripteroidea gestellt wird. Alle zuvor aus den Tendaguru-Schichten beschriebenen Taxa werden als nomina dubia angesehen. In Tendaguru sind Verteter der „Rhamphorhynchoidea“ und Dsungaripteroidea nachgewiesen. Diese systematische Zusammensetzung ist derjenigen anderer Flugsaurier-Vergesellschaftungen der späten Jura-Zeit ähnlich. Die Vielfalt und die weite Verbreitung der Dsungaripteroidea in Laurasia läßt darauf schließen, daß sich diese Flugsauriergruppe bereits in der späten Jura-Zeit erfolgreich durchgesetzt hatte. doi:10.1002/mmng.1999.4860020109</a

Entropy Bounds and Black Hole Remnants

We rederive the universal bound on entropy with the help of black holes while allowing for Unruh--Wald buoyancy. We consider a box full of entropy lowered towards and then dropped into a Reissner--Nordstr\"om black hole in equilibrium with thermal radiation. We avoid the approximation that the buoyant pressure varies slowly across the box, and compute the buoyant force exactly. We find, in agreement with independent investigations, that the neutral point generically lies very near the horizon. A consequence is that in the generic case, the Unruh--Wald entropy restriction is neither necessary nor sufficient for enforcement of the generalized second law. Another consequence is that generically the buoyancy makes only a negligible contribution to the energy bookeeping, so that the original entropy bound is recovered if the generalized second law is assumed to hold. The number of particle species does not figure in the entropy bound, a point that has caused some perplexity. We demonstrate by explicit calculation that, for arbitrarily large number of particle species, the bound is indeed satisfied by cavity thermal radiation in the thermodynamic regime, provided vacuum energies are included. We also show directly that thermal radiation in a cavity in $D$ dimensional space also respects the bound regardless of the value of $D$. As an application of the bound we show that it strongly restricts the information capacity of the posited black hole remnants, so that they cannot serve to resolve the information paradox.Comment: 12 pages, UCSBTH-93-2

Substantial and sustained improvements in blood pressure, weight and lipid profiles from a carbohydrate restricted diet: an observational study of insulin resistant patients in primary care

Hypertension is the second biggest known global risk factor for disease after poor diet; perhaps lifestyle interventions are underutilized? In a previous small pilot study, it was found that a low carbohydrate diet was associated with significant improvements in blood pressure, weight, ‘deprescribing’ of medications and lipid profiles. We were interested to investigate if these results would be replicated in a larger study based in ‘real world’ GP practice. 154 patients with type 2 diabetes or impaired glucose tolerance were recruited into an observational cohort study in primary care. The effects of a low carbohydrate diet sustained for an average of two years (interquartile range 10–32 months) on cardiovascular risk factors were examined. Results demonstrate significant and substantial reductions in blood pressure (mean reduction of systolic BP 10.9 mmHg (interquartile range 0–22 mmHg) (p &lt; 0.0001), mean reduction in diastolic BP 6.3 mmHg (interquartile range 0–12.8 mmHg) (p &lt; 0.0001) and mean weight reduction of 9.5 Kg (interquartile range 5–13 Kg) (p &lt; 0.0001) together with marked improvement in lipid profiles. This occurred despite a 20% reduction in anti-hypertensive medications. This novel and potentially highly effective dietary modification, done very cheaply alongside routine care, offers hope that should be tested in a large prospective trial

A Hydrophobic Gate in an Ion Channel: The Closed State of the Nicotinic Acetylcholine Receptor

The nicotinic acetylcholine receptor (nAChR) is the prototypic member of the `Cys-loop' superfamily of ligand-gated ion channels which mediate synaptic neurotransmission, and whose other members include receptors for glycine, gamma-aminobutyric acid, and serotonin. Cryo-electron microscopy has yielded a three dimensional structure of the nAChR in its closed state. However, the exact nature and location of the channel gate remains uncertain. Although the transmembrane pore is constricted close to its center, it is not completely occluded. Rather, the pore has a central hydrophobic zone of radius about 3 A. Model calculations suggest that such a constriction may form a hydrophobic gate, preventing movement of ions through a channel. We present a detailed and quantitative simulation study of the hydrophobic gating model of the nicotinic receptor, in order to fully evaluate this hypothesis. We demonstrate that the hydrophobic constriction of the nAChR pore indeed forms a closed gate. Potential of mean force (PMF) calculations reveal that the constriction presents a barrier of height ca. 10 kT to the permeation of sodium ions, placing an upper bound on the closed channel conductance of 0.3 pS. Thus, a 3 A radius hydrophobic pore can form a functional barrier to the permeation of a 1 A radius Na+ ion. Using a united atom force field for the protein instead of an all atom one retains the qualitative features but results in differing conductances, showing that the PMF is sensitive to the detailed molecular interactions.Comment: Accepted by Physical Biology; includes a supplement and a supplementary mpeg movie can be found at http://sbcb.bioch.ox.ac.uk/oliver/download/Movies/watergate.mp

Zero modes, entropy bounds and partition functions

Some recent finite temperature calculations arising in the investigation of the Verlinde-Cardy relation are re-analysed. Some remarks are also made about temperature inversion symmetry.Comment: 12 pages, JyTe

Robustness of RISMC Insights under Alternative Aleatory/Epistemic Uncertainty Classifications: Draft Report under the Risk-Informed Safety Margin Characterization (RISMC) Pathway of the DOE Light Water Reactor Sustainability Program

The Risk-Informed Safety Margin Characterization (RISMC) pathway is a set of activities defined under the U.S. Department of Energy (DOE) Light Water Reactor Sustainability Program. The overarching objective of RISMC is to support plant life-extension decision-making by providing a state-of-knowledge characterization of safety margins in key systems, structures, and components (SSCs). A technical challenge at the core of this effort is to establish the conceptual and technical feasibility of analyzing safety margin in a risk-informed way, which, unlike conventionally defined deterministic margin analysis, would be founded on probabilistic characterizations of uncertainty in SSC performance. In the context of probabilistic risk assessment (PRA) technology, there has arisen a general consensus about the distinctive roles of two types of uncertainty: aleatory and epistemic, where the former represents irreducible, random variability inherent in a system, whereas the latter represents a state of knowledge uncertainty on the part of the analyst about the system which is, in principle, reducible through further research. While there is often some ambiguity about how any one contributing uncertainty in an analysis should be classified, there has nevertheless emerged a broad consensus on the meanings of these uncertainty types in the PRA setting. However, while RISMC methodology shares some features with conventional PRA, it will nevertheless be a distinctive methodology set. Therefore, the paradigms for classification of uncertainty in the PRA setting may not fully port to the RISMC environment. Yet the notion of risk-informed margin is based on the characterization of uncertainty, and it is therefore critical to establish a common understanding of uncertainty in the RISMC setting

Fainting Fanconi syndrome clarified by proxy: a case report

BACKGROUND: Rare diseases may elude diagnosis due to unfamiliarity of the treating physicians with the specific disorder. Yet, advances in genetics have tremendously enhanced our ability to establish specific and sometimes surprising diagnoses. CASE PRESENTATION: We report a case of renal Fanconi syndrome associated with intermittent hypoglycemic episodes, the specific cause for which remained elusive for over 30 years, despite numerous investigations, including three kidney and one liver biopsy. The most recent kidney biopsy showed dysmorphic mitochondria, suggesting a mitochondrial disorder. When her son presented with hypoglycemia in the neonatal period, he underwent routine genetic testing for hyperinsulinemic hypoglycemia, which revealed a specific mutation in HNF4A. Subsequent testing of the mother confirmed the diagnosis also in her. CONCLUSION: Modern sequencing technologies that test multiple genes simultaneously enable specific diagnoses, even if the underlying disorder was not clinically suspected. The finding of mitochondrial dysmorphology provides a potential clue for the mechanism, by which the identified mutation causes renal Fanconi syndrome

Space VLBI at Low Frequencies

At sufficiently low frequencies, no ground-based radio array will be able to produce high resolution images while looking through the ionosphere. A space-based array will be needed to explore the objects and processes which dominate the sky at the lowest radio frequencies. An imaging radio interferometer based on a large number of small, inexpensive satellites would be able to track solar radio bursts associated with coronal mass ejections out to the distance of Earth, determine the frequency and duration of early epochs of nonthermal activity in galaxies, and provide unique information about the interstellar medium. This would be a "space-space" VLBI mission, as only baselines between satellites would be used. Angular resolution would be limited only by interstellar and interplanetary scattering.Comment: To appear in "Astrophysical Phenomena Revealed by Space VLBI", ed. H. Hirabayashi, P. Edwards, and D. Murphy (ISAS, Japan